FIG. 11 illustrates a hydraulic excavator 10, which is a work machine. The hydraulic excavator 10 includes a lower structure 11, an upper structure 12, a cab 13, a work equipment 14, and a power system 15 that includes an engine. The cab 13, the work equipment 14, and the power system 15 are mounted on the upper structure 12, which is rotatably mounted on the lower structure 11. The power system 15 is covered by a top cover 16, side doors 17, and other such components. Each side door 17 is attached, by hinges 18 so as to be freely openable and closable. The side door 17 is provided with a holding mechanism 19, which is illustrated in FIGS. 12 to 14 and serves to keep the side door 17 open.
When the side door 17 is closed, the conventional holding mechanism 19 illustrated in FIGS. 12 to 14 is stowed as illustrated in FIG. 13 in such a manner that a U-shaped hold-stay or rod 19s bridges respective holes of brackets 19a,19b, which are attached to an upper structure frame 12f. When the side door 17 is open, the hold-stay or rod 19s is hooked in the hole of the bracket 19a, which is attached to the upper structure frame 12f, and a hole of a bracket 19d, which is attached to the inner surface of the side door 17, so that the hold-stay or rod 19s bridges the bracket 19a and the bracket 19d as illustrated in FIG. 14 (e. g. see Japanese Laid-open Patent Publication No. 9-315347 (p 4, and FIG. 4) and Japanese Laid-open Patent Publication No. 2001-107627 (p 4, and FIG. 1) (“JP '627”)).
At that time, the side door 17 is locked in the open position by manually operating a single hold-stay or rod 19s. As a side door of a work machine is prone to bouncing back from the fully open position when it is opened, it is desirable from the perspective of better safety that the hold-stay or rod be automatically operated to be in the locked position.
In case of a structure for opening and closing the engine hood of a work machine, it is possible to provide the structure with a mechanism for automatically locking a hold-stay (e. g. see Japanese Laid-open Patent Publication No. 2009-113658 (pp 9-10, and FIGS. 7-9)). However, such a structure cannot be applied to a side door without modification.
According to the conventional structure, the side door 17 is locked in the open position by manually operating a single hold-stay or rod 19s. Therefore, in cases where the side door 17 is wide or heavy, an inadvertent or otherwise application of a force in such a direction as to close the door when the hold-stay or rod 19s is still in the locked position may deform the hold-stay or rod 19s, because the single hold-stay or rod 19s is unable to bear the force. On the other hand, should an attempt be made to open the door wider than the angle at which the door is stopped, a hinge plate described in JP '627 or other component may become deformed. Therefore, it is necessary to improve the durability of the hinge plate or such other components.
It is easy to provide each of the upper and lower hinges with a hold-stay or rod described in JP '627 if only for the purpose of improving the durability. However, as the vertical dimension of a work machine is large, it often happens that an operator cannot reach the hold-stay or rod of the upper hinge and has to prepare a ladder or the like, resulting in reduced working efficiency.
In order to solve the above problems, an object of the invention is to provide a hinge that enables a plurality of hold-stay members to be automatically locked when the door is fully open, thereby increasing the durability of the hinge, and also enables easy releasing of the plurality of hold-stay members. Another object of the invention is to provide a door unit equipped with this hinge.